Acute inflammation 2 Flashcards
(26 cards)
what is opsonization?
The process of coating a particle to target it for phagocytosis
what allows microorganisms to be recognised?
coated with opsonins
what do opsonins do?
bind to specific receptors on leucocytes and greatly enhance phagocytosis
what is phagocytosis?
the complex process by which phagocytes such as neutrophils and macrophages engulf and ingest microorganisms or other cells and foreign particles
what are the 3 steps of phagocytosis?
i. Recognition and Attachment
ii. Engulfment
iii. Killing and Degradation
what occurs of phagocytosis ?
neutrophils undergo apoptosis
Describe recognition and attachment.
Although attachment to specific receptors is not an absolute requirement, phagocytosis is typically initiated by recognition of particles by leucocyte surface receptors
Efficiency of phagocytosis is greatly enhanced when particles are opsonized
Describe engulfment.
Engulfment involves cytoplasmic extensions to flow around the particle resulting in complete ‘engulfment’ of the particle within a phagosome made by the cell membrane
This phagosome membrane then fuses with lysosomal membrane, resulting in discharge of the lysosome content into the phagolysosome
what two mechanism doe s killing of infectious agents occur?
- oxygen-dependent
- oxygen- independent
Describe the mechanism of oxygen-dependent?
Phagocytosis results in products of oxygen reduction which cause intracellular killing of micro-organisms
Describe the mechanism of oxygen-independent?
Via the action of substances in leucocyte granules eg Lysozyme which attacks bacterial coat
Defensins that are cytotoxic to microbes Acidic pH inside phagocytic vacuoles
after killing, what degrades the microorganism inside the phagolysosome?
acid hydrolase
where are the leucocytes products released to?
extracellular space aswell as the phagolysosome
what are the key products in neutrophils and macrophages?
- Lysosomal enzymes
- Oxygen derived active metabolites
- Products of arachidonic acid metabolism including prostaglandins and leukotrienes
what are the effects of lysosomal product release?
- ActivatescoagulationfactorXII
- Attracts other leucocytes into the area
- Damageslocaltissues
- Increases vascular permeability
- Pyrogens producing systemic fever
what are the macroscopic appearances of acute inflammation?
Necrotising – septic necrosis, bacterial putrefaction • Serous – thin protein rich fluid exudate
• Catarrhal – mucus hypersecretion
• Fibrinous – exudate contains plentiful fibrin
• Suppurative – production of pus
• Membranous – epithelium coated by fibrin
what is suppuration and what causes it?
Formation of pus –neutrophils, bacteria, cellular debris
• Causative stimulus almost always infective agent, eg pyogenic
bacteria such as staphylococci
what is an ulcer?
An ulcer is a local defect, or excavation, of the surface of an organ or tissue that is produced by the sloughing of inflammatory necrotic tissue
where are ulcers most frequently found in?
- Mucosa of the mouth, GI tract, GU tract
2. Low limbs (chronic ulcers) in those with circulatory disturbance
what are the beneficial effects of acute inflammation?
- Dilution of toxins- can be carried away by lymphatics
- Entry of antibodies- due to increased vascular permeability
- Stimulation of the immune response- fluid exudate containing antigens reaches local lymph nodes
- Fibrin Formation – impedes movement of micro-organisms 5. Delivery of nutrients and oxygen - aided by blood flow
- Transport of drugs – eg antibiotics
what are harmful effects of acute inflammation?
Digestion of normal tissues
• Swelling – eg laryngeal oedema, brain swelling
• Inappropriate inflammatory response – eg type I hypersensitivity
what are systemic effects of acute inflammation?
- Fever
- Constitutional Symptoms
- Weight Loss
- Reactive Hyperplasia of the Reticuloendothelial System
- Haematological Changes
what do most bacterial infections produce?
neutrophilia
what can viral infections produce?
lymphocytosis
